A friend had an '89 K1500 short bed. What a truck! SBC "383" conversion, revised diffs (gone were the little "swing out" fingers), 'twas a manual.
Oddly, the clutch slave was on the passenger's side. This necessitated a snaky hydraulic line.
I figured the transmission would be more popular in UK applications so GM put it on the right side.
Does your '91 have the "shared bulge" in the glove compartment? Half the bulge is in the back of the glove box and the other half bulges out the firewall. It contained the new electronics. My friend's fuel system came with a tuned chip and a more stock one.
Does your engine have the separate, nascent fuel control system?
'Twas a 5' X 6" X1.5" black plastic thing on its own bracket ahead of and to the right of the carb?
HERE'S THE KICKER: Upon doing a head job (thank me very much!) and installing headers the engine ran badly.
We tried adjusting the valves several times. My pal tried replacing the push rods and more.
It turns out the BATTERY CABLE had a tap off to power the fuel system.
The battery cable's clamp was full of corrosion. A new cable cured the horrid condition.
His vehicle also had a muffler AHEAD of the air cleaner's snorkel.
I love your hood mounted bug deflector too but it does seem a bit aged. It might shatter if you ever go above 55 mph!